Stop hair from falling through emitter mesh
Enabling collision on the emitter doesn't work on the hair system, yet (2.77). 
To achieve collision, you have to do a workaround with a collision mesh:
1. You have to duplicate your model. 
2. remove the hair particle system on the duplicated Mesh.
3. Exclude the duplicated mesh from rendering (uncheck rendering in the outliner). 4. Enable collision on the duplicated mesh.

You may need to tweak the settings a bit though.